Need to relate deaths to prevalence, severity, and treatment in different populations

There seems little doubt that the prevalence of asthma in children and adolescents is increasing all over the world,¹ and several epidemics of deaths in the past 30 years have aroused vigorous debate about the possible causes. Awareness of the importance of decreasing death rates in the 1980s led to the development of asthma management plans or guidelines, first at national level, such as those for Australia² and England,³ then at international level, and now globally.⁴ The aim of these plans was to achieve better care. One of the signs of this is decreasing death rates, especially in young people, in whom deaths are mostly avoidable (as shown by the falling rates in the presence of increasing prevalence of the disease). Since it is widely stated in the lay press that death rates from asthma are rising worldwide, the paper by Campbell et al in this week's BMJ (p 1439), showing that the mortality from asthma is decreasing in those under 65 years in England and Wales, is timely.⁵

Caution is needed in interpreting data from death certificates, especially in elderly people,⁶ as fashions for diagnosing airway diseases change. However, in people under 35 death certificates are thought to more accurately reflect asthma …